The present invention relates to an apparatus for blocking the passage of solid materials into or through a channel while permitting the passage of fluid. More particularly, the present invention relates to such an apparatus that also automatically releases accumulated solid materials under predetermined release conditions in which release is deemed to take priority over continued blocking, and automatically re-close after the accumulated solid materials have been released. The present invention also relates to a method (sometimes referred to herein as process) for controlling the passage of solid material into or through a channel; and more particularly, to such a method that utilizes an apparatus embodying the present invention to block the passage of solid materials, hold the accumulated solid materials until the occurrence of predetermined release conditions, automatically release the solid materials, automatically resume blocking and accumulating solid materials, and automatically repeat the process upon recurrence of the predetermined release conditions.
As used in this specification, “solid material” means any item of natural or man-made solid material, including any comprised of trash, debris, vegetation, one or more sticks, one or more rocks, all or part of an animal, or any combination thereof, that has at least one dimension larger than a predetermined size. Such solid material is also referred to herein singly and plurally simply as “trash.” Selection of the predetermined (maximum) size for the solid material that will be permitted to pass through an aperture is often based on use of a hypothetical model of the solid material. The hypothetical model typically is a spherical shape that is rigid (neither elastic nor flexible). Of course, many forms of solid material are not spherical in shape or are not rigid; and those solid materials can sometimes pass through an aperture that is smaller than the solid material's maximum dimension, which may be due to the solid material's orientation upon reaching the aperture or to its compressibility or flexibility. Thus, an aperture that is intended to block solid materials of a predetermined size should not be expected to stop all solid materials with a dimension larger than that size.
As used in this specification, “channel” (whether used alone or directly after “fluid” or “fluid-flow”) means any inlet, catch basin, channel, conduit, pipe, culvert, tube or any other man-made or natural confinement, or any system comprising some or all of these elements, through which fluid flows on at least some occasions. Channels, particularly drainage channels, often include a catch basin. The catch basin is typically located near the channel's beginning point; that is, near the point at which fluid first enters the channel system.
As used in this specification “fluid” means any fluid, or combination of fluids, that is normally or reasonably expected to be carried by the channel in which the apparatus is installed.
Solid materials tend to be moved by fluid and thereby enter into channels that collect or direct the flow of the fluid. It is generally desirable to minimize the amount of solid materials in the channel that are too large for the channel to move throughout its length during light or moderate flow periods. It is also desirable to minimize the amount of solid materials that pass through the channel and are large enough to create an environmental, aesthetic, health, or other problem at the discharge end of the channel. On the other hand, it is desirable for channels to be available for receiving and moving large amounts of fluid during heavy flow periods. The need for these desirable features is particularly apparent when considered in the context of a street or highway storm drain system.
Streets and highways frequently have curb inlets leading to catch basins as the initial entry points of drainage systems for collecting and draining water and other fluids that would otherwise accumulate in and ultimately flood the street or highway. It is desirable to minimize the entry of solid materials that are larger than a relatively small size, in order to reduce the frequency needed for cleaning such materials out of the system and the potential for animals or even small children entering through the inlets.
It may be observed that most curb inlets have no effective means for blocking the entry of trash. There have been ideas put forward that involve installation of a trash blocking device at the inlet but typically those devices require manual cleaning or removal to relieve the damming effect of an accumulation of trash during periods of heavy fluid flow. (See, e.g., U.S. Pat. No. 4,986,693, issued to Salberg et al. on Jan. 22, 1991; U.S. Pat. No. 5,702,595, issued to Mossberg on Dec. 30, 1997; U.S. Pat. No. 6,017,166, issued to Mossberg on Jan. 25, 2000; and, U.S. Pat. No. 6,402,942, issued to Cardwell et al. on Jun. 11, 2002.) The accumulation of trash during dry, light, or moderate flow periods is inconsequential because the accumulated materials do not significantly impede the flow of a modest volume of fluid into the drainage system. During such periods, street and highway maintenance personnel have no immediate need to clear the curb inlets and are at liberty to do so according to a predetermined schedule without significant risk of a flood occurring.
However, during periods of heavy flow, due to storms or other events that produce substantial amounts of fluid in the streets and highways, it is imperative that any significant impediment to the flow of such fluid into the drainage system be removed. These heavy flow periods often commence unexpectedly or on very short notice and, in some geographical areas, frequently. Thus, installation of most previously proposed blocking devices into curb inlets would put maintenance personnel under extreme pressure to mount an intensive and expensive effort to remove the blocking devices whenever heavy flow periods occur. Removal of such blocking devices generally requires personnel to expend substantial time and, in some cases, to use expensive equipment in order to access and remove the connecting means and the devices.
Nevertheless, such removal is necessary because the trash accumulated at the face of the blocking devices significantly impedes the large volume of fluid that is flowing into the drain system, thus causing a damming effect. Also, the blocking devices will continue to block and accumulate the additional trash that is being carried with the large volume of fluid, exacerbating the damming effect. Therefore, unless agencies that have responsibility for street and highway maintenance and/or flood control either forgo the benefits of having blocking devices or expend large sums for personnel and equipment to immediately remove the blocking devices every time a heavy flow period threatens or commences, the accumulations at the entrances to their drainage systems are very likely to cause substantial flooding.
It has been suggested that a blocking device made of elastic plastic material is needed to overcome the prohibitive cost, weight, and installation difficulties, found in blocking devices made of metal or other non-plastic material. And, further, that the prior devices made of metal or other non-plastic material are not particularly suitable for installation within a curb inlet and generally do not, without human assistance, clear the accumulated trash during periods of heavy flow. It has also been contended that attaching the heavy components of metal blocking devices with bolts anchored within the inlet or catch basin will weaken and over-stress that structure. (See U.S. Pat. No. 6,015,489, issued to Allen et al. on Jan. 18, 2000, which discloses a plastic self-relieving curb inlet filter that is secured by adhesive along its top edge within the curb inlet and is sufficiently elastic to flex inward in response to increasing pressure and unflex toward its closed position as the pressure is reduced.) Such a device offers advantages that may be achieved by the use of plastic and adhesive materials. However, the advantages also appear limited because of the use of those materials. The strength, flexibility and elasticity of plastics and adhesives may be adversely affected by repeated flexing and extended exposure to environmental conditions such as sun, air, water, and extreme temperature variations (ranging from above 100 degrees Fahrenheit to well below 0 degrees Fahrenheit in some geographical areas). A secure bond may be difficult to achieve or maintain in circumstances where the surface (generally made of concrete) suffers from irregularities, impurities, or mechanical weaknesses; and, if achieved, may be difficult to remove without some damage to the surface or the device. And, the efficacy of the device in opening and closing is dependent on the elasticity of the material used. Thus, if a very elastic material is used, the device may open with little pressure applied, such as during periods of light to medium fluid flow when remaining closed is generally desired. And, if a very inelastic material is used, the device may not open fully even when the initial resistance is overcome by a large pressure (the degree of resistance increasing with the degree of flexure), which is generally when full opening is most desired. Such a device, therefore, provides no effective means of control to assure the blockage is maintained when that is most desirable and released when that is most desirable.
Consequently, it appears that prior efforts at blocking the passage of trash in channels, and particularly in catch-basin curb inlets, were directed primarily at the use of heavy metal or other heavy materials for devices that were expensive and difficult to install and remove. It also appears that those efforts did not address or suggest a practical and economical solution to the problem of trash accumulation and blockage during heavy flow periods when the passage of fluid needs to be maximized. Apparently perceiving that metals and similar materials were unsuitable for solving the problem, a proposal was made in at least one patent (discussed above) to use elastic plastic material for making a device that would open and close in response to the pressure caused by flow/debris accumulation. However, it may be seen that elastic plastic materials do not have many of the advantages afforded by metals and other strong and substantially rigid materials, and that the prior art using such elastic plastic materials has significant deficiencies, including lack of effective control over the release of accumulated trash.
The present invention provides advantages not afforded by the relevant prior art and does so in a manner that appears both unanticipated by and inconsistent with suggestions in the relevant prior art.